1. Field of the Invention
The invention relates to a method and apparatus for measuring the quantity of a fluid flowing through a pipe by means of nuclear magnetic spin resonance, where magnetizable nuclei of the fluid are aligned by a d-c magnetic field and are synchronized by an a-c magnetic field, so that a subsequent evaluation of the magnetization of the nuclei can be performed.
2. Description of the Prior Art
From U.S. Pat. Nos. 3,551,794, 3,559,044 and 2,562,632 it is known that conclusions can be drawn from the nuclear magnetization as to a quasi "mean" flow velocity. For this purpose, pulsed synchronization of the aligned nuclei, for example, makes possible the transit time measurement of passing mass components. This permits the establishment of a relationship with the flow velocity. The accuracy of the measurement is limited, however, as the velocity distribution over the cross section of the pipe is not taken into consideration. The aforementioned heretofore known method can therefore furnish usable volume thoughput results only by means of calibration measurements, which must be carried out for all possible flow operating conditions. Thus, the only advantage remaining over mechanical flow meters is that the interior of the fluid-carrying pipe need not be disturbed by inserts that might be corrosion-sensitive. Also, the heretofore known method can be used only for the determination of the volume flow rate of single-phase fluids.